So forcing everyone to change their meeting place to a venue with a unisex bathroom only is not political, but a trans woman using a woman’s bathroom is political?
Nobody is calling for unisex bathrooms as far as I know, so it can't really be called a political choice. It is just practical - there isn't a consensus about who should get a special bathroom. How can there be a special bathroom if we don't know who is supposed to be using it?
Also, Helen still wants to be called Helen and still wants to be referred to as a she. By this logic, everyone must go by they/them? Or what?
I don't see how to get away from that one, there is a fundamental rift between the people who think individuals control their identity and the people who think that identity is constructed by someone's peers (see also, shaking off an unwelcome nickname).
But that is an inescapable problem that has dogged humanity since before we were a species so good luck excluding it from any space. If it flares up and diplomacy can't smooth it out then some organiser is just going to have to make a call.